Tertiary alkyl azomethine copolymers



United States Patent No Drawing. Filed Dec. 30, 1957, Ser. No. 705,785 10 (Ilaims. (Cl. 250-471) This invention relates to novel compositions of matter which are effective as viscosity index improvers and detergents in lubricant compositions. More particularly, the invention pertains to improved lubricant compositions containing the reaction products of tertiary alkyl azomethines with copolymers of isopropenyl acetoacetate.

Within recent years it has become common practice to impart improved properties to lubricants through the use of various types of additives or addition agents. Lubricating oils employed in internal combustion engines such as automotive and diesel engines require the use of one or more addition agents to improve their serviceability under certain adverse operating conditions. Among the more important additives employed are the type which function to prevent the formation and accumulation of sludge and varnish-like coatings on pistons and cylinder walls of the engine. Such additives which have the property of maintaining clean engines are referred to as detergent-type addition agents. Other addition agents in common usage are known as viscosity index improvers. These additives function to improve the viscosity-temperature characteristics of the lubricant in which they are employed, said relationship commonly being expressed in the art as the viscosity index of the oil.

It is an object of this invention to provide novel reaction products of tertiary alkyl azomethines. Another object of this invention is to provide novel addition agents which when added to a lubricant will improve both the detergent properties and the viscosity index thereof. Still another object is to provide lubricant compositions possessing improved detergency and viscosity-temperature characteristics. Other objects and advantages of the invention will become apparent in the following description thereof.

The above objects, among others, are achieved in accordance with this invention by incorporating in a lubricating oil from about 0.01% to about 10% of an oil soluble addition agent which is the reaction product of from about 1% to about 40% by weight of (A) a tertiary alkyl azomethine, hereinafter defined, with about 99% to about 60% of (B) a copolymer of isopropenyl acetoacetate and an organic comonomer or mixture of comonomers capable of addition copolymerization, said copolymer having a molecular Wei ht within the range from about 10,000 to about 125,000, and preferably within the range from about 20,000 to about 70,000, the mole ratio of isopropenyl acetoacetate to other comonomer or comonomers in said copolymer being within the range from about 1:100 and 1:1, and preferably from about 1:5 to about 1:2, said reaction being conducted at a temperature within the range from about 60 C. to about 150 C., and preferably from about 80 C. to about 125 C.

The azomethines which are useful in this invention have the general formula wherein R R and R represent the same or different alkyl radicals, said azomethine having from 5 to about 30, and preferably from about 9 to about 16, carbon atoms in the molecule. Specific examples of azomethines included within this class and which are suitable for use in the invention are t-butyl azomethine, t-octyl azomethice inc, t-nonyl azomethine, t-dodecyl azomethine, t-octadecyl azomethine, t-tetracosyl azomethine and mixtures thereof. These azomethines, also known as aldimines, can readily be prepared in good yield by reacting formaldehyde with the desired talkyl amines, drying, and distilling as is described in US. Patent No. 2,582,128 issued Januany 8, 1952, to Melvin D. Hurwitz.

The copolymer used as a reactant in forming the prodnets of the present invention is a copolymer of isopropenyl acetoacetate and a comonomer or mixture of comonomers capable of addition and copolymerization. isopropenyl acetoacetate has the formula I I group. The preferred monomers are those containing a terminal ethylenic group, i.e., a

group, wherein at least one of the valence bonds is linked to a negative group, and the other bond is linked to hydrogen or a hydrocarbon group. The preferred monomers may therefore be defined as vinylidene compounds (which term is intended to include vinyl compounds) wherein there is attached to the vinylidene roup at least one negative group, such as an aryl group (for example, as in styrene, alpha-mcthyl styrene, chlorinated styrenes, 3-methyl styrene, 3,4,5-trimethyl styrene, etc.); an acyloxy group (vinyl acetate, vinyl butyrate, vinyl decanoate, vinyl octadecanoate, etc.); an alkoxy group (vinyl ethyl ether, vinyl butyl ether, vinyl decyl ether, vinyl octadecyl ether, etc.); an aroyloxy group (vinyl benzoate, vinyl toluate, etc.); an aryloxy group (vinyl phenyl ether, vinyl xylyl ethers, etc.); a carbalkoxy group (butyl acrylate, hexyl methacrylate, octyl acrylate, nonyl methacrylate, ootadecyl acrylate, octadecyl methacrylate, etc.), etc. For use in preparing the lubricant additives of this invention, copolymers formed from comonomers containing only carbon and hydrogen atoms (for example, styrene and alkylated styrenes) or only carbon, hydrogen, and oxygen atoms (for example, unsubstituted vinyl esters and ethers) and isopropenyl aeetoacetate are preferred.

The preferred monomers (i.e., vinylidene monomers) can be used in admixture with other monomers containing internal ethylenic unsaturation which do not readily homopolymerize but which will copolymerize with the isopropenyl acetoacetate and the vinylidene monomers. The preferred internally unsaturated compounds are esters of butenedioic acids having the general formula 0 H R; 0 II I H CC=O-( J 0R1 on.

wherein R and R represent the same or different alkyl radicals having from about 4 to about 22 carbon atoms, and preferably from about 6 to about 12 carbon atoms,

aoaaeis and R is selected from the group consisting of hydrogen and a methyl radical. Examples of such internally unsaturated compounds are dibutyl fumarate, di-iso-octyl fumarate, dioctadecyl fumarate and the corresponding esters of maleic, citraconic and mesaconic acids.

The copolymers used in forming the products of this invention must be oil soluble. In order to achieve this end it is preferred that the cornonomers used in forming copolymers with isopropenyl acetoacetate each have from about 6 to about 30 carbon atoms, and preferably about 10 to about 24 carbon atoms in the molecule. In any given case oil solubility can readily be increased by adjusting the ratio of the reactants so as to increase the proportion of the more soluble monomer in the copolymer, for example the proportion of di-iso-octyl fumarate in a mixture of the same, styrene, and isopropenyl acetoacetate, or by increasing the chain length of the substituent hydrocarbon groups, for example, the ester group when an acrylate or methacrylate is used or the side chain when an alkyl styrene is used. Suitable mole ratios of isopropenyl acetoacetate to other monomers in the copolymer range from about 1:100 to about 1:1 and preferably from about 1:5 to about 1:2. When a mixture of vinylidene compounds and internally unsaturated compounds (e.g., butenedioic acid esters such as maleates or fumarates) is used, the mole ratio of the vinylidene compounds to the other monomers should be within the range from about 1:2 to about 4:1 and preferably from about 1:1 to about 2:1 in order to insure the formation of a copolymer.

The copolymerization can be carried out by any of the methods known to the art, i.e. in bulk, in solution or in emulsion. Bulk and solution polymerization are preferred, however. A particularly useful expedient is solution polymerization in which the solvent is a lubricating oil similar to that in which the additive is to be used, e.g., an SAE 10 to SAE base oil when the additive is to be used in an automotive crankcase oil. The reaction with azomethine can then be carried out with the copolymer in solution, resulting in a concentrate of the final reaction product in oil solution which requires no purification and which is easily handled and dispensed.

In preparing the copolymers used in this invention there can be employed as a catalyst any compound which is capable of providing stable free radicals under the conditions of the reaction. Examples of such catalysts are peroxy compounds, for example, organic peroxides, peroxy salts, hydroperoxides, etc., such as t-butyl peroxide, acetyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, ethyl peroxy carbonate, and the like, and

azo compounds such as a,a-azodiisobutyronitrile, dimethyl and diethyl a,a'-azodiisobutyrate, etc. Such initiators can be used in a concentration of about 0.001% to 0.5% by weight. In addition, polymerization may also be initiated by the use of ultra-violet light as well as by the use of heat alone.

In general, the range of polymerization reaction temperatures employed in producing the copolymers varies between about 80 C. and 150 C. and is preferably within the range from about 100 C. to about 130 C. It will be understood that the polymerization temperature selected will usually be varied according to the nature and amount of the particular monomers and catalysts, if any, used, the desired polymerization pressure and the molecular weight of the products which are desired. Likewise the time for polymerization will be dependent on similar factors and can range over a period from about 2 hours to about 96 hours, as will be apparent to one skilled in the art.

The isopropenyl acetoacetate copolymers are reacted with the azomethine in accordance with the invention by heating a mixture of the reactants, optionally in the presence of an inert diluent or solvent such as a petroleum lubricating oil fraction, at a temperature within the range from about C. to about 150 C., and preferably from about to about C., for a period of time from about 1 to about 20 hours, and preferably from about 2 to about 10 hours. The reactants are used in such proportions that the azornethine constitutes from about 1% to about 40%, and preferably from about 2% to about 25%, of the combined weight of the azomethine and copolymer used. At the end of the reaction period any excess, unreacted azomethine can easily be removed by blowing with nitrogen until the characteristic azomethine odor disappears.

The following examples are illustrative of my invention, and are not intended to be limiting.

EXAMPLE 1 The preparation of the copolymers used in accordance with the invention is illustrated by the preparation of a copolymer of isopropenyl acetoacetate and n-lauryl methacrylate, as follows: A mixture of 3 ml. isopropenyl acetoacetate, 27 ml. n-lauryl methacrylate and 0.1 ml. t-butyl hydroperoxide was heated at 100 C. for 16 hours and at C. for 6 hours. The light yellow copolymer resulting had a specific viscosity, 1% solution in toluene at 20 C., of 0.126.

EXAMPLE 2 The isopropenyl acetoacetate used in these examples was prepared as follows: A mixture of 212 ml. acetone, 39 ml. diketene, 0.5 ml. pyridine and 0.5 g. anhydrous zinc sulfate was stirred and refluxed for 20 hours. The product was filtered and distilled, yielding 18.5 g. isopropenyl acetoacetate, boiling range 77.5-80 C. at 3.7 mm. Hg, 11 1.4678, density (20 C.) 1.0769.

EXAMPLE 3 A mixture of the copolymer prepared in Example 1 and 2 ml. Primene JMR azomethine (prepared from formaldehyde and Primene IM-R, a commercial product of Rohm and Haas Co. which is a mixture of tertiary amines consisting principally of t-C1 H37NH2 to t-C24I I49NH2, neutral equivalent 303, boiling range 262- 315 0, sp. gr. 0.845 and 11 1.460) was heated at 100 C. for 1 /2 hours. The light orange product con tained 0.359% N; a 1% solution in toluene had a specific viscosity (20 C.) of 0.13.

EXAMPLE 4 A mixture of 2 ml. isopropenyl acetoacetate, 16 m1. 2- ethylhexyl acrylate, and 0.1 ml. t-butyl hydroperoxide was heated 16 hours at 100 C. and 6 hours at 125 0, giving a very viscous yellow copolymer. This was cooled to 100 0., treated with 1.5 ml. Primene 81-R azomet-hine (prepared from formaldehyde and Primene 81-R, a commercial product of Rohm and Haas Co. which is a mixture of tertiary amines consisting principally of t-C12H25NH2 to t-'C15H31NH2, Hutra1 equivalent boiling range 223-240 C., sp. gr. 0.812, and m 1.423) and heated at 100 C. for 1 /2 hours. The odor of the azomethine had completely disappeared. The light orange product contained 0.488% N; a 1% solution in toluene had a specific viscosity (20 C.) of 0.15.

EXAMPLE 5 A mixture of 4 ml. isopropenyl acetoacetate, 14 ml. styrene, 24 ml. di-iso-octyl fumarate, and 0.1 ml. t-butyl hydroperoxide was heated 16 hours at 100 C. and 6 hours at 125 C., giving a very viscous yellow copolymer. This was cooled to 100 C., 2 ml. t-octyl azomethine added, and the mixture heated 1 /2 hours at 100 C. All odor of azomethine had disappeared by this time. The light orange copolymer contained 0.415% N. A 1% solution in toluene had a specific viscosity (20 C.) of 0.20.

The reaction products of the above examples were tested for their effectiveness as viscosity index improvers at a concentration of 2% by weight in a solvent extracted SAE 5 base oil. The results are given in the following The detergent properties of the reaction products of my invention are demonstrated by the data in Table II, which are the results of the carbon suspension test (C. B. Biswell et al., Ind. Eng. Chem, 47, 1598, 1601 (1955)). The products were tested at 0.5 concentration in 70 cc. kerosene with three grams of a paste containing 20% carbon black in a heavy white oil base, stirring the mixture five minutes in a 100 cc. graduate in a Herschel demulsibility tester at room temperature (25 C.). After 5 days (120 hours) the percentage of carbon black which had settled out was recorded.

Table II Percent charcoal settled Product: after 120 hours None 90 (in 4 hours). Example 1 90 (in 6 hours). Example 3 0.

Example 4 0. Example 5 0.

It can be seen from the above data that the novel products of my invention are effective both as viscosity index improvers and detergents in oils. .By contrast, a comparison in Table II of the product of Example 1 with those of Examples 3, 4, and 5 shows that copolymers of isopropenyl acetoacetate prior to reaction with azomethine (Example 1) possess no detergent properties whatsoever.

The products of this invention can be used in lubricating oils in concentrations of from about 0.01% to about and preferably from about 0.5% to about 5% by weight. Although the present invention has been illustrated by the use of these products in mineral lubricating oils it is not restricted thereto. Other lubricating oil bases can be used, such as hydrocarbon oils, both natural and synthetic, for example, those obtained by the polymerization of olefins, as well as synthetic lubricating oils of the alkylene Oxide type and the polycarboxylic acid ester type, such as the oil soluble esters of adipic acid, sebacic acid, azelaic acid, etc. It is also contemplated that various other well known additives, such as antioxidants, anti-foaming agents, pour point depressors, extreme pressure agents, antiwear agents, etc., may be incorporated in lubricating oils containing the additives of my invention.

Concentrates of a suitable oil base containing more than 10%, for example up to 50% or more, of the copolymers of this invention alone or in combination with other additives can be used for blending with hydrocarbon oils or other oils in the proportions desired for the particular conditions of use to give a finished product containing from about 0.01% to about 10% of the reaction products of this invention.

Unless otherwise stated, the percentages given herein and in the claims are percentages by weight.

While 1 have described my invention by reference to specific embodiments thereof, the same are given by way of illustration only. Modifications and variations will be apparent from my description to those skilled in the art.

Having described my invention, 1 claim:

1. An oil-soluble product obtained by reacting, at a temperature in the range of from about 60 C. to about 150 C., from about 1% to about 40% by weight of tertiary alkyl azomethine having from 5 to 30 carbon atoms and having the formula:

wherein R R and R are alkyl, and from about 60% to about 99% by weight of an isopropenyl acetoacetatecontaining copolymer having a molecular weight within the range of from about 10,000 to about 125,000 said isopropenyl acetoacetate-containing copolymer being prepared by the copolymerization at a temperature in the range of C. to C. of isopropenyl acetoacetate and a substituted-hydrocarbon comonomer and having a mole ratio of isopropenyl aoetoacetatezsubstituted=hydrocarbon comonomer in the range of from about 1:100 to about 1:1, said substituted-hydrocarbon comonomer having terminal ethylenic unsaturation and from 6 to 30 carbon atoms and having as the substituent a negative group selected from the class consisting of aryl, acyloxy, alkoxy, aroyloxy, aryloxy and carbalkoxy, said substituent being attached to the unsaturated carbon of said terminal ethylenic unsaturation.

2. The product of claim 1 wherein said azomethine is t-octyl azomethine.

3. The product of claim 1 wherein said copolymer has a molecular weight within the range from about 20,000 to about 70,000.

4. The product of claim 1 wherein said comonomer is n-laury1 methacrylate.

5. An oil-soluble product obtained by reacting, at a temperature in the range of from about 60 C. to about 150 C., from about 1% to about 40% by weight of tertiary alkyl azomethine having from 5 to about 30 carbon atoms and having the formula:

wherein R R and R are alkyl, and from about 60% to about 99% by weight of an isopropenyl acetoacetatecontaining copolymer having a molecular weight within the range of from about 10,000 to about 125,000 said isopropenyl acetoacetate-containing copolymer being prepared by the copolymerization at a temperature in the range of 80 C. to 150 C. of isopropenyl acetoacetate and a substituted-hydrocarbon comonomer and having a mole ratio of isopropenyl acetoacetate:substituted-hydrocarbon comonomer in the range of from about 12100 to about 1:1, said substituted-hydrocarbon comonomer having terminal ethylenic unsaturation and from 10 to 24 carbon atoms and having as the substituent a negative group selected from the class consisting of aryl, acyloxy, alkoxy, aroyloxy, aryloxy and carbalkoxy, said substituent being attached to the unsaturated carbon of said terminal ethylenic unsaturation.

6. The copolymer of claim 5 which has as a monomeric unit a diester of butenedioic acid, said diester having the formula:

wherein R and R represent alkyl having from about 4 to about 22 carbon atoms and R is selected from the class consisting of hydrogen and methyl, the mole ratio of said substituted-hydrocarbon comonomer to said diester being within the range of from about 1:2 to about 4: 1, said copolymer being formed by said copolymerization with said diester in admixture with said isopropenyl acetoacetate and said substituted-hydrocarbon comonomer at said copolymerization temperature.

7. The product of claim 6 wherein said diester is a diester of fumaric acid.

8. The product of claim 6 in which said diester is di-isooctyl fumarate.

9. The product of claim 6 in which said substitutedhydrocarbon comonomer is styrene.

10. The product of claim 6 in which said azomethine is t-octyl azomethine.

References Cited in the file of this patent UNITED STATES PATENTS Lynch Mar. 16, Giammaria Oct. 9, Catlin Feb. 12, Giammaria Nov. 4, Catlin et a1 Dec. 27, Popkin Oct. 22,

OTHER REFERENCES Tomayo et a1.: Chem. Abst., 42, 1571 (1948). 

5. AN OIL-SOLUBLE PRODUCT OBTAINED BY REACTING, AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 60*C. TO ABOUT 150*C., FROM ABOUT 1% TO ABOUT 40% BY WEIGHT OF TERTIARY ALKYL AZOMETHINE HAVING FROM 5 T ABOUT 30 CARBON ATOMS AND HAVING THE FORMULA:
 6. THE COPOLYMER OF CLAIM 5 WHICH HAS AS A MONOMERIC UNIT A DIESTER OF BUTENEDIOIC ACID, SAID DIESTER HAVING THE FORMULA:
 9. THE PRODUCT OF CLAIM 6 IN WHICH SAID SUBSTITUTEDHYDROCARBON COMONOMER IS STYRENE. 